Ommochromes, such as the ommatin xanthommatin, are one of the two types of eye pigments in D. melanogaster. Their biosynthesis starts in the cytosol with the conversion of L-tryptophan to 3-hydroxy-L-kynurenine which, following its import into pigment granules (known as ommochromasomes), undergoes condensation to produce xanthommatin. Ommochromes function in various processes including vision, colour patterning and L-tryptophan detoxification. (Adapted from PMID:29989284.)